// SPDX-License-Identifier: GPL-2.0 /* * Dynamic function tracing support. * * Copyright (C) 2007-2008 Steven Rostedt * * Thanks goes to Ingo Molnar, for suggesting the idea. * Mathieu Desnoyers, for suggesting postponing the modifications. * Arjan van de Ven, for keeping me straight, and explaining to me * the dangers of modifying code on the run. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef CONFIG_DYNAMIC_FTRACE static int ftrace_poke_late = 0; int ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex) { /* * Need to grab text_mutex to prevent a race from module loading * and live kernel patching from changing the text permissions while * ftrace has it set to "read/write". */ mutex_lock(&text_mutex); ftrace_poke_late = 1; return 0; } int ftrace_arch_code_modify_post_process(void) __releases(&text_mutex) { /* * ftrace_make_{call,nop}() may be called during * module load, and we need to finish the text_poke_queue() * that they do, here. */ text_poke_finish(); ftrace_poke_late = 0; mutex_unlock(&text_mutex); return 0; } static const char *ftrace_nop_replace(void) { return x86_nops[5]; } static const char *ftrace_call_replace(unsigned long ip, unsigned long addr) { return text_gen_insn(CALL_INSN_OPCODE, (void *)ip, (void *)addr); } static int ftrace_verify_code(unsigned long ip, const char *old_code) { char cur_code[MCOUNT_INSN_SIZE]; /* * Note: * We are paranoid about modifying text, as if a bug was to happen, it * could cause us to read or write to someplace that could cause harm. * Carefully read and modify the code with probe_kernel_*(), and make * sure what we read is what we expected it to be before modifying it. */ /* read the text we want to modify */ if (copy_from_kernel_nofault(cur_code, (void *)ip, MCOUNT_INSN_SIZE)) { WARN_ON(1); return -EFAULT; } /* Make sure it is what we expect it to be */ if (memcmp(cur_code, old_code, MCOUNT_INSN_SIZE) != 0) { WARN_ON(1); return -EINVAL; } return 0; } /* * Marked __ref because it calls text_poke_early() which is .init.text. That is * ok because that call will happen early, during boot, when .init sections are * still present. */ static int __ref ftrace_modify_code_direct(unsigned long ip, const char *old_code, const char *new_code) { int ret = ftrace_verify_code(ip, old_code); if (ret) return ret; /* replace the text with the new text */ if (ftrace_poke_late) text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL); else text_poke_early((void *)ip, new_code, MCOUNT_INSN_SIZE); return 0; } int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { unsigned long ip = rec->ip; const char *new, *old; old = ftrace_call_replace(ip, addr); new = ftrace_nop_replace(); /* * On boot up, and when modules are loaded, the MCOUNT_ADDR * is converted to a nop, and will never become MCOUNT_ADDR * again. This code is either running before SMP (on boot up) * or before the code will ever be executed (module load). * We do not want to use the breakpoint version in this case, * just modify the code directly. */ if (addr == MCOUNT_ADDR) return ftrace_modify_code_direct(ip, old, new); /* * x86 overrides ftrace_replace_code -- this function will never be used * in this case. */ WARN_ONCE(1, "invalid use of ftrace_make_nop"); return -EINVAL; } int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { unsigned long ip = rec->ip; const char *new, *old; old = ftrace_nop_replace(); new = ftrace_call_replace(ip, addr); /* Should only be called when module is loaded */ return ftrace_modify_code_direct(rec->ip, old, new); } /* * Should never be called: * As it is only called by __ftrace_replace_code() which is called by * ftrace_replace_code() that x86 overrides, and by ftrace_update_code() * which is called to turn mcount into nops or nops into function calls * but not to convert a function from not using regs to one that uses * regs, which ftrace_modify_call() is for. */ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr) { WARN_ON(1); return -EINVAL; } int ftrace_update_ftrace_func(ftrace_func_t func) { unsigned long ip; const char *new; ip = (unsigned long)(&ftrace_call); new = ftrace_call_replace(ip, (unsigned long)func); text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL); ip = (unsigned long)(&ftrace_regs_call); new = ftrace_call_replace(ip, (unsigned long)func); text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL); return 0; } void ftrace_replace_code(int enable) { struct ftrace_rec_iter *iter; struct dyn_ftrace *rec; const char *new, *old; int ret; for_ftrace_rec_iter(iter) { rec = ftrace_rec_iter_record(iter); switch (ftrace_test_record(rec, enable)) { case FTRACE_UPDATE_IGNORE: default: continue; case FTRACE_UPDATE_MAKE_CALL: old = ftrace_nop_replace(); break; case FTRACE_UPDATE_MODIFY_CALL: case FTRACE_UPDATE_MAKE_NOP: old = ftrace_call_replace(rec->ip, ftrace_get_addr_curr(rec)); break; } ret = ftrace_verify_code(rec->ip, old); if (ret) { ftrace_bug(ret, rec); return; } } for_ftrace_rec_iter(iter) { rec = ftrace_rec_iter_record(iter); switch (ftrace_test_record(rec, enable)) { case FTRACE_UPDATE_IGNORE: default: continue; case FTRACE_UPDATE_MAKE_CALL: case FTRACE_UPDATE_MODIFY_CALL: new = ftrace_call_replace(rec->ip, ftrace_get_addr_new(rec)); break; case FTRACE_UPDATE_MAKE_NOP: new = ftrace_nop_replace(); break; } text_poke_queue((void *)rec->ip, new, MCOUNT_INSN_SIZE, NULL); ftrace_update_record(rec, enable); } text_poke_finish(); } void arch_ftrace_update_code(int command) { ftrace_modify_all_code(command); } /* Currently only x86_64 supports dynamic trampolines */ #ifdef CONFIG_X86_64 #ifdef CONFIG_MODULES #include /* Module allocation simplifies allocating memory for code */ static inline void *alloc_tramp(unsigned long size) { return module_alloc(size); } static inline void tramp_free(void *tramp) { module_memfree(tramp); } #else /* Trampolines can only be created if modules are supported */ static inline void *alloc_tramp(unsigned long size) { return NULL; } static inline void tramp_free(void *tramp) { } #endif /* Defined as markers to the end of the ftrace default trampolines */ extern void ftrace_regs_caller_end(void); extern void ftrace_regs_caller_ret(void); extern void ftrace_caller_end(void); extern void ftrace_caller_op_ptr(void); extern void ftrace_regs_caller_op_ptr(void); extern void ftrace_regs_caller_jmp(void); /* movq function_trace_op(%rip), %rdx */ /* 0x48 0x8b 0x15 */ #define OP_REF_SIZE 7 /* * The ftrace_ops is passed to the function callback. Since the * trampoline only services a single ftrace_ops, we can pass in * that ops directly. * * The ftrace_op_code_union is used to create a pointer to the * ftrace_ops that will be passed to the callback function. */ union ftrace_op_code_union { char code[OP_REF_SIZE]; struct { char op[3]; int offset; } __attribute__((packed)); }; #define RET_SIZE 1 + IS_ENABLED(CONFIG_SLS) static unsigned long create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) { unsigned long start_offset; unsigned long end_offset; unsigned long op_offset; unsigned long call_offset; unsigned long jmp_offset; unsigned long offset; unsigned long npages; unsigned long size; unsigned long *ptr; void *trampoline; void *ip; /* 48 8b 15 is movq (%rip), %rdx */ unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 }; unsigned const char retq[] = { RET_INSN_OPCODE, INT3_INSN_OPCODE }; union ftrace_op_code_union op_ptr; int ret; if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { start_offset = (unsigned long)ftrace_regs_caller; end_offset = (unsigned long)ftrace_regs_caller_end; op_offset = (unsigned long)ftrace_regs_caller_op_ptr; call_offset = (unsigned long)ftrace_regs_call; jmp_offset = (unsigned long)ftrace_regs_caller_jmp; } else { start_offset = (unsigned long)ftrace_caller; end_offset = (unsigned long)ftrace_caller_end; op_offset = (unsigned long)ftrace_caller_op_ptr; call_offset = (unsigned long)ftrace_call; jmp_offset = 0; } size = end_offset - start_offset; /* * Allocate enough size to store the ftrace_caller code, * the iret , as well as the address of the ftrace_ops this * trampoline is used for. */ trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *)); if (!trampoline) return 0; *tramp_size = size + RET_SIZE + sizeof(void *); npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE); /* Copy ftrace_caller onto the trampoline memory */ ret = copy_from_kernel_nofault(trampoline, (void *)start_offset, size); if (WARN_ON(ret < 0)) goto fail; ip = trampoline + size; memcpy(ip, retq, RET_SIZE); /* No need to test direct calls on created trampolines */ if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { /* NOP the jnz 1f; but make sure it's a 2 byte jnz */ ip = trampoline + (jmp_offset - start_offset); if (WARN_ON(*(char *)ip != 0x75)) goto fail; ret = copy_from_kernel_nofault(ip, x86_nops[2], 2); if (ret < 0) goto fail; } /* * The address of the ftrace_ops that is used for this trampoline * is stored at the end of the trampoline. This will be used to * load the third parameter for the callback. Basically, that * location at the end of the trampoline takes the place of * the global function_trace_op variable. */ ptr = (unsigned long *)(trampoline + size + RET_SIZE); *ptr = (unsigned long)ops; op_offset -= start_offset; memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE); /* Are we pointing to the reference? */ if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0)) goto fail; /* Load the contents of ptr into the callback parameter */ offset = (unsigned long)ptr; offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE; op_ptr.offset = offset; /* put in the new offset to the ftrace_ops */ memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE); /* put in the call to the function */ mutex_lock(&text_mutex); call_offset -= start_offset; memcpy(trampoline + call_offset, text_gen_insn(CALL_INSN_OPCODE, trampoline + call_offset, ftrace_ops_get_func(ops)), CALL_INSN_SIZE); mutex_unlock(&text_mutex); /* ALLOC_TRAMP flags lets us know we created it */ ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP; set_vm_flush_reset_perms(trampoline); if (likely(system_state != SYSTEM_BOOTING)) set_memory_ro((unsigned long)trampoline, npages); set_memory_x((unsigned long)trampoline, npages); return (unsigned long)trampoline; fail: tramp_free(trampoline); return 0; } void set_ftrace_ops_ro(void) { struct ftrace_ops *ops; unsigned long start_offset; unsigned long end_offset; unsigned long npages; unsigned long size; do_for_each_ftrace_op(ops, ftrace_ops_list) { if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) continue; if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { start_offset = (unsigned long)ftrace_regs_caller; end_offset = (unsigned long)ftrace_regs_caller_end; } else { start_offset = (unsigned long)ftrace_caller; end_offset = (unsigned long)ftrace_caller_end; } size = end_offset - start_offset; size = size + RET_SIZE + sizeof(void *); npages = DIV_ROUND_UP(size, PAGE_SIZE); set_memory_ro((unsigned long)ops->trampoline, npages); } while_for_each_ftrace_op(ops); } static unsigned long calc_trampoline_call_offset(bool save_regs) { unsigned long start_offset; unsigned long call_offset; if (save_regs) { start_offset = (unsigned long)ftrace_regs_caller; call_offset = (unsigned long)ftrace_regs_call; } else { start_offset = (unsigned long)ftrace_caller; call_offset = (unsigned long)ftrace_call; } return call_offset - start_offset; } void arch_ftrace_update_trampoline(struct ftrace_ops *ops) { ftrace_func_t func; unsigned long offset; unsigned long ip; unsigned int size; const char *new; if (!ops->trampoline) { ops->trampoline = create_trampoline(ops, &size); if (!ops->trampoline) return; ops->trampoline_size = size; return; } /* * The ftrace_ops caller may set up its own trampoline. * In such a case, this code must not modify it. */ if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) return; offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS); ip = ops->trampoline + offset; func = ftrace_ops_get_func(ops); mutex_lock(&text_mutex); /* Do a safe modify in case the trampoline is executing */ new = ftrace_call_replace(ip, (unsigned long)func); text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL); mutex_unlock(&text_mutex); } /* Return the address of the function the trampoline calls */ static void *addr_from_call(void *ptr) { union text_poke_insn call; int ret; ret = copy_from_kernel_nofault(&call, ptr, CALL_INSN_SIZE); if (WARN_ON_ONCE(ret < 0)) return NULL; /* Make sure this is a call */ if (WARN_ON_ONCE(call.opcode != CALL_INSN_OPCODE)) { pr_warn("Expected E8, got %x\n", call.opcode); return NULL; } return ptr + CALL_INSN_SIZE + call.disp; } void prepare_ftrace_return(unsigned long ip, unsigned long *parent, unsigned long frame_pointer); /* * If the ops->trampoline was not allocated, then it probably * has a static trampoline func, or is the ftrace caller itself. */ static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec) { unsigned long offset; bool save_regs = rec->flags & FTRACE_FL_REGS_EN; void *ptr; if (ops && ops->trampoline) { #if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) && \ defined(CONFIG_FUNCTION_GRAPH_TRACER) /* * We only know about function graph tracer setting as static * trampoline. */ if (ops->trampoline == FTRACE_GRAPH_ADDR) return (void *)prepare_ftrace_return; #endif return NULL; } offset = calc_trampoline_call_offset(save_regs); if (save_regs) ptr = (void *)FTRACE_REGS_ADDR + offset; else ptr = (void *)FTRACE_ADDR + offset; return addr_from_call(ptr); } void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec) { unsigned long offset; /* If we didn't allocate this trampoline, consider it static */ if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) return static_tramp_func(ops, rec); offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS); return addr_from_call((void *)ops->trampoline + offset); } void arch_ftrace_trampoline_free(struct ftrace_ops *ops) { if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) return; tramp_free((void *)ops->trampoline); ops->trampoline = 0; } #endif /* CONFIG_X86_64 */ #endif /* CONFIG_DYNAMIC_FTRACE */ #ifdef CONFIG_FUNCTION_GRAPH_TRACER #if defined(CONFIG_DYNAMIC_FTRACE) && !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) extern void ftrace_graph_call(void); static const char *ftrace_jmp_replace(unsigned long ip, unsigned long addr) { return text_gen_insn(JMP32_INSN_OPCODE, (void *)ip, (void *)addr); } static int ftrace_mod_jmp(unsigned long ip, void *func) { const char *new; new = ftrace_jmp_replace(ip, (unsigned long)func); text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL); return 0; } int ftrace_enable_ftrace_graph_caller(void) { unsigned long ip = (unsigned long)(&ftrace_graph_call); return ftrace_mod_jmp(ip, &ftrace_graph_caller); } int ftrace_disable_ftrace_graph_caller(void) { unsigned long ip = (unsigned long)(&ftrace_graph_call); return ftrace_mod_jmp(ip, &ftrace_stub); } #endif /* CONFIG_DYNAMIC_FTRACE && !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */ /* * Hook the return address and push it in the stack of return addrs * in current thread info. */ void prepare_ftrace_return(unsigned long ip, unsigned long *parent, unsigned long frame_pointer) { unsigned long return_hooker = (unsigned long)&return_to_handler; int bit; /* * When resuming from suspend-to-ram, this function can be indirectly * called from early CPU startup code while the CPU is in real mode, * which would fail miserably. Make sure the stack pointer is a * virtual address. * * This check isn't as accurate as virt_addr_valid(), but it should be * good enough for this purpose, and it's fast. */ if (unlikely((long)__builtin_frame_address(0) >= 0)) return; if (unlikely(ftrace_graph_is_dead())) return; if (unlikely(atomic_read(¤t->tracing_graph_pause))) return; bit = ftrace_test_recursion_trylock(ip, *parent); if (bit < 0) return; if (!function_graph_enter(*parent, ip, frame_pointer, parent)) *parent = return_hooker; ftrace_test_recursion_unlock(bit); } #ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct ftrace_regs *fregs) { struct pt_regs *regs = &fregs->regs; unsigned long *stack = (unsigned long *)kernel_stack_pointer(regs); prepare_ftrace_return(ip, (unsigned long *)stack, 0); } #endif #endif /* CONFIG_FUNCTION_GRAPH_TRACER */